1. Field of the Invention
This invention relates to a rotor of a rotary electric machine which features reduced ventilation drive loss and increased efficiency.
2. Description of the Prior Art
A conventional salient-pole rotor of a synchronous motor has been constructed as shown in a vertical section view of FIG. 1 and a sectional plan view of FIG. 2. Namely, FIGS. 1 and 2 illustrate the rotor of a vertical shaft type machine with rotary shaft 1, rotor spider 2, rim 3 which is inserted and adhered to the rotor spider and which constitutes a yoke of the rotor, and a plurality of ventilation ducts 4 formed in a radial direction in the rim. Ventilation gaps are defined by a plurality of duct pieces 5 and gap rings 6. Bolts 7 fasten the rim 3 with nuts 8. A plurality of salient pole cores 10 consist of a laminate of thin steel plates, which are fastened by bolts, and which are adhered to the outer periphery of the rim 3; Salient pole 9 consists of the pole core 10 and the field coil 11, and fan 12 is mounted on the rim 3.
Stator frame 13 supports stator core 14 and has ventilation ducts 15 in the radial direction, stator coil 16, enclosure 17, rotor 18, which consists of the above-mentioned members 1 to 12, stator 19, which consists of the above-mentioned members 13 to 17, with air gap 20 defined between the rotor 18 and the stator 19.
In the above-mentioned conventional device, when the rotor 18 rotates, the cooling air introduced by the fan 12 cools the ends of field coils 11, and flows along the ends of the stator coil 16 as indicated by arrows, cooling the coils. Further, the cooling air introduced at the side of inner diameter of the rotor spider 2 flows through the ventilation ducts 4, and flows through the neighboring field coils 11 as indicated by arrows, cooling them. The cooling air flowing through the field coils 11 gushes through the air gap 20 being assisted by the fan action created by salient poles, and then flows through ventilation ducts 15 formed in the stator to cool the stator coil 16 and the stator core 14.
Here, mechanical loss of the rotor 18 can be divided into windage loss and bearing loss. The windage loss is further divided into ventilation drive loss that results from the ventilation, and friction loss that results from the friction with the surrounding air. With the above-mentioned conventional construction, however, the cooling air flowing through the poles 9 gushes into the air gap 20 maintaining nearly the same angular velocity as the rotor 18. Namely, the cooling air gushes into the air gap 20 having a large angular momentum. The angular velocity, however, becomes zero when the cooling air enters into ventilation ducts 15 of the stator 19 after passing through the air gap 20. Therefore, the large angular momentum of the cooling air turns directly into ventilation drive loss, and makes it difficult to obtain a high efficiency.